With fluid flow paths for which transfusion, blood transfusion or the like is performed in the medical field, to make it possible to connect and disconnect a syringe, transfusion bag or the like, a needleless connector is sometimes used. This needleless connector is constituted provided with a drug solution flow path inlet and outlet at one side and the other side of the lengthwise direction of the housing, and with an elastic valve body equipped with a slit at the inlet attached. The outlet of the drug solution flow path can be connected with a catheter, and by a catheter inserted in a blood vessel being connected with the drug solution flow path outlet, the drug solution flow path and the blood vessel are in communication.
Also, the drug solution flow path is switched from a blocked state to a communicating state by opening a slit by the elastic valve body being elastically deformed by the male luer inserted from the inlet of the drug solution flow path. Drug solution administration to the patient is performed by having a drug solution flow into the needless connector interior from a syringe or the like connected to the male luer in this kind of communicating state with the drug solution flow path. When drug solution administration is completed, the male luer is removed from the housing, and by the slit of the elastic valve body closing, the drug solution flow path is blocked by the elastic valve body, and the male luer is disconnected from the drug solution flow path connected to the blood vessel or the like.
However, with the needleless connector, when removing the male luer from the slit, there is the risk that blood will enter from the blood vessel to the catheter connected to that drug solution flow path (backflow), and that blood coagulation will occur. In light of that, there is demand for a needleless connector for which it is possible to prevent backflow of blood when removing the male luer from the slit.
In light of that, with PCT Japanese Translation Patent Publication No. JP-A-2006-515220 (Patent Document 1) and the like, a hollow elastic body (piston) is arranged in the accommodation part of the housing, and by the hollow elastic body being pressed by a male luer such as of a syringe or the like, compression deformation occurs in the axial direction on the tube shaped piston wall, and the drug solution flow path is switched to the communicating state. Then, by the male luer being removed, the deformation of the hollow elastic body is cancelled, the drug solution flow path is switched to the blocked state, and backflow of blood is prevented.
However, with the structure of Patent Document 1, there is the problem that with things such as blocking by the piston wall for which the lower channel has deformed or the like, switching to the communicating state for the drug solution flow cannot be realized with sufficient reliability.
Furthermore, the tube shaped piston wall is compressed in the axial direction by the pressing force of the male luer, but when the piston wall is made thin and deforms easily, it is difficult to obtain sufficient shape restoring force based on the elasticity of the item itself, and an auxiliary spring such as a coil spring or the like is needed. Meanwhile, when the piston wall is made thick to obtain sufficient shape restoring force by the elasticity of the piston wall itself, there is the risk of problems such as it being difficult for compression deformation to occur with the piston wall, making it difficult to do the operation of switching the drug solution flow path to the communicating state, or the piston wall overall deforming so as to bulge to the outer circumference side, blocking the drug solution flow path or the like.
As noted in FIG. 7 and FIG. 8 of U.S. Pat. No. 5,730,418 (Patent Document 2), it is also conceivable to stabilize the hollow elastic body deformation mode by doing something like making the part to be deformed by pressing by the male luer at the hollow elastic body a bellows shape in advance or the like. However, in this case as well, due to the pressure fluctuation that accompanies the volume change of the drug solution flow path, the problem of blood backflow before blocking of the drug solution flow path is not eliminated. Furthermore, since the bellows part of the hollow elastic body undergoes general compression deformation in the axial direction, it is difficult to realize both ease of deformation and sufficient shape restorability, and it was difficult to stably and quickly perform switching between the drug solution flow path communicating state and the blocked state.